This invention relates generally to unmanned, self-propelled vehicles and more particularly to a vehicle such as a robot and methods for traveling across and turning on a surface with compound curves.
People frequently use unmanned, self-propelled vehicles such as robots to perform a variety of functions that would be difficult or dangerous for a person to perform. For example many people frequently use robots to retrieve or dispose an explosive device or inspect or work in an environment that could kill or injure a person. People also frequently use robots to inspect or work in locations that typically are hard to access or are inaccessible by a person such as inspecting a pipeline.
Unfortunately, because robots typically propel themselves to a work site, use of most conventional unmanned, self-propelled vehicles is typically significantly limited by the ability of the robot to propel itself over a surface. For example, surfaces that include compound curves or three dimensional curves, abrupt inclinations or declinations, steps or gaps can cause conventional robots to become significantly less stable, i.e., more likely to lose their preferred orientation relative to the surface, as they traverse the surface or turn on it. In addition, surfaces that are slippery can cause conventional robots to easily lose a significant portion, if not all, of their traction to the surface. If either happens while traversing an incline or inverted surface such as a ceiling, such a loss of traction could cause the robot to fall. Such a fall could seriously damage the robot, its payload if it has any, or the surface or other components of the structure the robot is traversing.
Another problem with conventional robots is they tend to scrub the surface as they traverse and turn on it. This can cause undesirable scratches on the surface. For example, the skin or windshield of a commercial airplane must remain free from scratches because of the high stress imposed on it during flight. If a scratch does occur, the skin or windshield is often replaced at great expense in both time and money.
Yet another problem with conventional robots is they tend to bounce or jerk as they propel themselves across a surface. This can be a significant problem during inspection of, for example, a commercial airplane""s crown skin or structurexe2x80x94the top part of the airplane""s bodyxe2x80x94because most inexpensive non-destructive inspection techniques require the inspection apparatus to remain a substantially constant distance from the surface being inspected. Because of this requirement, most inspections of an airplane typically include erecting a scaffold, which can be time consuming, for an inspector to stand on prior to inspecting the structure.
In one aspect of the invention, a traction unit includes a frame, a plurality of trucks attached to the frame and operable to propel the frame across a surface, and a plurality of adherence members attached to and movable relative to the frame and operable to releasably secure the frame to the surface. Each adherence member includes a foot attached to a body that is operable to extend the foot toward the surface and retract the foot from the surface. The traction unit also includes a plurality of corresponding return mechanisms attached to the frame and operable to move the adherence members to respective return positions. With the adherence members merely attaching the unit to the surface and the trucks merely propelling the unit across the surface, the unit can traverse and turn on compound curved surfaces.
In another aspect of the invention, a control unit makes sure that at least one adherence member is attached to the surface while the unit traverses the surface.